A multifunctional stop-wagon retarder for railway wagon is disclosed in Chinese Pat. No. ZL92232912.5. This retarder can reduce the speed of a wagon, stop a wagon, or prevent a stalled wagon from running away. And it will do work on a wagon at low speed, and be locked by a wagon at high speed. However, the retarder has disadvantages. The structure of its uni-directional return unit makes the normal returning speed of sliding cylinder unadjustable and therefore, the retarder can not have different control levels. The term "control level" means the time necessary for the sliding cylinder of the stop-wagon retarder to return to its original position after it is deflected downwards by a wheel of the wagon. It's locking control valve can not regulate the locking speed and different thresholds for controlling the locking speed can not be set. The connection mode of the positioning unit is complicated and its components are liable to come off, which affects locking precision. And the exhaust hole located rather low in the housing harms its water prevention performance. In addition, existing disposal method for stop-wagon retarders adopts centralized method to dispose large retarder group which can not achieve good retardation on wagons.